Voice coil motors and magnetic circuits therefor

Abstract

A magnet of rectangular prism or parallelepiped prism shape is disposed on a yoke having a triangle shape or a frusto-triangular shape to construct a magnetic circuit for a voice coil motor. The magnetic circuits facilitate positioning and holding of a moving coil, and the voice coil motor is improved in positioning precision of a magnetic head.

1. A magnetic circuit for a voice coil motor, comprising a
 magnetic material yoke and magnet means disposed thereon, wherein 
 the magnetic material yoke is configured to a triangular shape, a frusto-triangular shape in which the apex of a triangle is truncated or round, or an arcuate, crescent or semi-circular ring shape in which the bottom of a triangle at its center is recessed or cut-off in a semi-circular, triangle or apex-rounded triangular form, 
 the magnet means on said yoke consists of a single magnet piece of rectangular prism or parallelepiped prism shape, and 
 the single magnet piece is disposed on said yoke such that the longitudinal direction of said single magnet piece is parallel to a bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke. 
 
     
     
       2. A magnetic circuit for a voice coil motor, comprising:
 a pair of opposed magnetic material yokes; and 
 magnet means disposed on at least one of the pair of yokes so that the magnet means faces the other yoke, wherein 
 the magnetic material yoke is configured to a triangular shape, a frusto-triangular shape in which the apex of a triangle is truncated or round, or an arcuate, crescent or semi-circular ring shape in which the bottom of a triangle at its center is recessed or cut-off in a semi circular, triangle or apex-rounded triangular form, 
 the magnet means disposed on a said yoke consists of a single magnet piece of rectangular prism or parallelepiped prism shape, and 
 the single magnet piece is disposed on yoke such that the longitudinal direction of said magnet piece is parallel to a bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke. 
 
     
     
       3. The magnetic circuit of  claim 2 , wherein the magnet
 means is disposed on each of the pair of yokes so that the magnet means face each other, 
 each said magnet means disposed on a respective yoke consists of a single magnet piece of rectangular prism or parallelepiped prism shape, and 
 each single magnet piece is disposed on said yoke such that the longitudinal direction of said magnet piece is parallel to a bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke. 
 
     
     
       4. A voice coil motor comprising:
 a magnetic circuit comprising a pair of opposed magnetic material yokes, and magnet means disposed on at least one of the pair of yokes so that the magnet means faces the other yoke, wherein 
 the magnetic material yoke is configured to a triangular shape, a frusto-triangular shape in which the apex of a triangle is truncated or round, or an arcuate crescent or semi-circular ring shape in which the bottom of a triangle at its center is recessed or cut-off in a semi circular, triangle or apex-rounded triangular form, 
 the magnet means disposed on a said yoke consists of a single magnet piece of rectangular prism or parallelepiped prism shape, and 
 the single magnet piece is disposed on yoke such that the longitudinal direction of said magnet piece is parallel to bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke; and 
 a moving coil located between the magnet piece and the other yoke. 
 
     
     
       5. The voice coil motor of  claim 4 , wherein
 the magnet means are disposed on each of the pair of yokes so that the magnet means face each other 
 each said magnet means disposed on a respective yoke consists of a single magnet piece of rectangular prism or parallelepiped prism shape, and 
 each single magnet piece is disposed on said yoke such that the longitudinal direction of said magnet piece is parallel to a bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke.